1. Technical Background
The present invention relates generally to medical devices, and more particularly to a catheter having a portion coated with fullerenes, and therapeutic methods for making and using the same.
2. Discussion
Medical catheters are used in a variety of therapeutic applications, including esophageal catheters, urinary catheters, and intravascular catheters for procedures such as angioplasty. By way of example, the present invention will be described in relation to vascular catheters, and in particular intravascular balloon catheters. However, it should be understood that the present invention relates to any catheter or catheter system incorporating fullerenes, and is not limited to balloon catheters or any other type of catheter.
For example, most balloon catheters have a relatively long and flexible tubular shaft defining one or more passages, called lumens, an inflatable balloon at a forward or distal end connected to an inflation lumen extending through the shaft, leading to a proximal hub at the other end for connecting the shaft lumens to various equipment. Examples of this type of balloon catheter are shown in U.S. Pat. No. 5,304,197, entitled xe2x80x9cBalloons For Medical Devices And Fabrication Thereof,xe2x80x9d issued to Pinchuk et al. on Apr. 19th, 1994, and U.S. Pat. No. 5,370,615, entitled xe2x80x9cBalloons Catheter For Angioplasty,xe2x80x9d issued to Johnson on Dec. 6, 1994.
A common treatment method for using such a balloon catheter is to advance the catheter into the body of a patient, by directing the catheter distal end through an incision and along a body passage, until the balloon is located within the desired site. The term xe2x80x9cdesired sitexe2x80x9d refers to the location in the patient""s body currently selected for treatment by a health care professional. After the balloon is disposed within the desired site, it can be selectively inflated for one of two basic purposes. First, the balloon may be used to temporarily block or occlude the body passage at a relatively low pressure, as in the case of a balloon made of elastic or compliant material. Second, the balloon can press outward on the wall of the body passage at relatively high pressure to a relatively constant diameter, as in the case of an inelastic or non-compliant balloon material.
This outward pressing of a constriction or narrowing at the desired site in a body passage is intended to partially or completely re-open or dilate that passageway or lumen, increasing its inner diameter or cross-sectional area. In the case of a blood vessel, this procedure is referred to as angioplasty, and it encourages greater blood flow through the newly expanded vessel. The narrowing of the lumen is called a lesion or stenosis, and may be formed of hard plaque or viscous thrombus.
Nearly one million angioplasties were performed worldwide in 1997 to treat vascular disease, including coronary, neurological and peripheral blood vessels partially or totally blocked or narrowed by a stenosis.
Unfortunately, within approximately six months after angioplasty, the lumen at the angioplasty site may re-close or narrow again. This phenomenon is called restenosis, and may occur in as many as 35% of percutaneous transluminal angioplasty patients. Restenosis may require an additional procedure, such as another angioplasty, drug therapy treatment, or surgery including bypass graft. It is of course desirable to prevent or limit the occurrence of restenosis, especially since some patients may not be preferred candidates for another interventional treatment.
One method of limiting restenosis is to permanently implant a cylindrical metal scaffold, referred to as a stent, into the vessel to hold the lumen open and improve blood flow. The presence of a stent tends to keep the blood vessel open longer, but their use can be limited by various factors, including size and location of the blood vessel, a complicated or tortuous vessel pathway, etc. Also, even a vessel with a stent may eventually develop restenosis.
A possible cause for restenosis is the proliferation of smooth muscle cells at the site of the lesion. In other words, a site where tissue has grown in the past, in the form of a collection of smooth muscle cells before angioplasty, may tend to accumulate cells at that location again. Accordingly, it is desirable to prevent or limit accumulation of these fast-replicating smooth muscle cells, in an effort to prevent restenosis.
It has been discovered that the local presence of oxygen radicals (or other reactive oxygen species) in the vicinity of a stenosis may kill smooth muscle cells, or inhibit their future accumulation. It is therefore desirable to provide a system or device and method for generating these oxygen radicals at the desired site within the patient""s body.
It is possible that the presence of a newly discovered type of material may generate oxygen radicals or other reactive oxygen species when activated by exposure to light. This new class of materials is called xe2x80x9cfullerenes,xe2x80x9d and they represent a previously unknown third form or allotrope of carbon. The other two carbon allotropes have been known for most of recorded history: graphite and diamond.
The family of fullerene materials includes a symmetrical hollow spherical molecule containing 60 carbon atoms (C60), and also various asymmetrical forms, including carbon atoms in groups of 70, 76, 78, 82, 84, 90, and 96. The entire class of materials is named after the designer of the geodesic dome, R. Buckminster Fuller, because the spherical C60 looks like a geodesic dome or soccer ball. Accordingly, C60 is called Buckminsterfullerene or xe2x80x9cbucky balls.xe2x80x9d The bucky ball is the only molecule of a single atom that forms a hollow spheroid shape, in geometric terms a xe2x80x9ctruncated icosahedon.xe2x80x9d
In 1985, Richard Smalley, Robert Curl, and Harold Kroto, won the Nobel Prize in chemistry for their work with fullerenes. This work led to various articles and patents, including U.S. Pat. No. 5,300,203, entitled xe2x80x9cProcess For Making Fullerenes By The Laser Evaporation Of Carbon,xe2x80x9d issued to Smalley on Apr. 5, 1994. A variety of compositions and different applications for fullerenes are described in many patents, including U.S. Pat. No. 5,172,278, entitled xe2x80x9cBuckminsterfullerenes For Optical Limiters,xe2x80x9d issued to Tutt on Dec. 15, 1992, and U.S. Pat. No. 5,561,026, entitled xe2x80x9cPhotosensitive Materials Comprising Fullerenes,xe2x80x9d issued to Aoki on Oct. 1, 1996.
It is accordingly a general object of the present invention to provide a catheter system incorporating fullerenes for performing or facilitating a medical procedure.